[OpenCL] Guard atomic_double with cl_khr_int64_*

It is necessary to guard atomic_double type according to
https://www.khronos.org/registry/OpenCL/specs/3.0-unified/html/OpenCL_C.html#_footnotedef_54.
Platform that disable cl_khr_int64_base_atomics and
cl_khr_int64_extended_atomics will have compiling errors even if
atomic_double is not used.

Patch by Haonan Yang.

Differential Revision: https://reviews.llvm.org/D119398